[Xen-devel] Re: [PATCH 2/6] MCE: Not GP fault when guest write non 0s or 1s to MCA CTL MSRs.

[Christoph Egger <Christoph.Egger@xxxxxxx>]

On Thursday 28 January 2010 06:55:53 Jiang, Yunhong wrote:
> Not GP fault when guest write non 0s or 1s to MCA CTL MSRs.
>
> a) For Mci_CTL MSR, Guest can write any value to it. When read back, it
> will be ANDed with the physical value. Some bit in physical value can be 0,
> either because read-only in hardware (like masked by AMD's Mci_CTL_MASK),
> or because Xen didn't enable it. If guest write some bit as 0, while that
> bit is 1 in host, we will not inject MCE corresponding that bank to guest,
> as we can't distinguish if the MCE is caused by the guest-cleared bit.
>
> b) For MCG_CTL MSR, guest can write any value to it. When read back, it
> will be ANDed with the physical value. If guest does not write all 1s. In
> mca_ctl_conflict(), we simply not inject any vMCE to guest if some bit is
> set in physical MSR while is cleared in guest 's vMCG_CTL MSR.
>
> Signed-off-by: Jiang, Yunhong <yunhong.jiang@xxxxxxxxx>
>
>
> diff -r b2a7600b71cc xen/arch/x86/cpu/mcheck/mce.c
> --- a/xen/arch/x86/cpu/mcheck/mce.c   Tue Jan 26 00:52:19 2010 +0800
> +++ b/xen/arch/x86/cpu/mcheck/mce.c   Tue Jan 26 00:57:19 2010 +0800
> @@ -30,6 +30,11 @@ unsigned int nr_mce_banks;
>  unsigned int nr_mce_banks;
>
>  static uint64_t g_mcg_cap;
> +
> +/* Real value in physical CTL MSR */
> +static uint64_t h_mcg_ctl = 0UL;
> +static uint64_t *h_mci_ctrl;
> +int firstbank;

The physical MSRs are per physical cpu-core on AMD CPUs.
The data structure does not reflect this.

Other than that this patch is fine with me.

Christoph


>
>  static void intpose_init(void);
>  static void mcinfo_clear(struct mc_info *);
> @@ -642,6 +647,21 @@ void mcheck_init(struct cpuinfo_x86 *c)
>               break;
>       }
>
> +    if ( !h_mci_ctrl )
> +    {
> +        h_mci_ctrl = xmalloc_array(uint64_t, nr_mce_banks);
> +        if (!h_mci_ctrl)
> +        {
> +            dprintk(XENLOG_INFO, "Failed to alloc h_mci_ctrl\n");
> +            return;
> +        }
> +        /* Don't care banks before firstbank */
> +        memset(h_mci_ctrl, 0xff, sizeof(h_mci_ctrl));
> +        for (i = firstbank; i < nr_mce_banks; i++)
> +            rdmsrl(MSR_IA32_MC0_CTL + 4*i, h_mci_ctrl[i]);
> +    }
> +    if (g_mcg_cap & MCG_CTL_P)
> +        rdmsrl(MSR_IA32_MCG_CTL, h_mcg_ctl);
>      set_poll_bankmask(c);
>       if (!inited)
>               printk(XENLOG_INFO "CPU%i: No machine check initialization\n",
> @@ -708,7 +728,8 @@ int mce_rdmsr(uint32_t msr, uint64_t *va
>              *val);
>          break;
>      case MSR_IA32_MCG_CTL:
> -        *val = d->arch.vmca_msrs.mcg_ctl;
> +        /* Always 0 if no CTL support */
> +        *val = d->arch.vmca_msrs.mcg_ctl & h_mcg_ctl;
>          mce_printk(MCE_VERBOSE, "MCE: rdmsr MCG_CTL 0x%"PRIx64"\n",
>              *val);
>          break;
> @@ -723,7 +744,8 @@ int mce_rdmsr(uint32_t msr, uint64_t *va
>          switch (msr & (MSR_IA32_MC0_CTL | 3))
>          {
>          case MSR_IA32_MC0_CTL:
> -            *val = d->arch.vmca_msrs.mci_ctl[bank];
> +            *val = d->arch.vmca_msrs.mci_ctl[bank] &
> +                    (h_mci_ctrl ? h_mci_ctrl[bank] : ~0UL);
>              mce_printk(MCE_VERBOSE, "MCE: rdmsr MC%u_CTL 0x%"PRIx64"\n",
>                       bank, *val);
>              break;
> @@ -805,13 +827,6 @@ int mce_wrmsr(u32 msr, u64 val)
>      switch ( msr )
>      {
>      case MSR_IA32_MCG_CTL:
> -        if ( val && (val + 1) )
> -        {
> -            mce_printk(MCE_QUIET, "MCE: val \"%"PRIx64"\" written "
> -                     "to MCG_CTL should be all 0s or 1s\n", val);
> -            ret = -1;
> -            break;
> -        }
>          d->arch.vmca_msrs.mcg_ctl = val;
>          break;
>      case MSR_IA32_MCG_STATUS:
> @@ -855,14 +870,6 @@ int mce_wrmsr(u32 msr, u64 val)
>          switch ( msr & (MSR_IA32_MC0_CTL | 3) )
>          {
>          case MSR_IA32_MC0_CTL:
> -            if ( val && (val + 1) )
> -            {
> -                mce_printk(MCE_QUIET, "MCE: val written to MC%u_CTL "
> -                         "should be all 0s or 1s (is %"PRIx64")\n",
> -                         bank, val);
> -                ret = -1;
> -                break;
> -            }
>              d->arch.vmca_msrs.mci_ctl[bank] = val;
>              break;
>          case MSR_IA32_MC0_STATUS:
> @@ -1162,6 +1169,23 @@ void intpose_inval(unsigned int cpu_nr,
>      (r) <= MSR_IA32_MC0_MISC + (nr_mce_banks - 1) * 4 && \
>      ((r) - MSR_IA32_MC0_CTL) % 4 != 0)       /* excludes MCi_CTL */
>
> +int mca_ctl_conflict(struct mcinfo_bank *bank, struct domain *d)
> +{
> +    int bank_nr;
> +
> +    if ( !bank || !d || !h_mci_ctrl )
> +        return 1;
> +
> +    /* Will MCE happen in host if If host mcg_ctl is 0? */
> +    if ( ~d->arch.vmca_msrs.mcg_ctl & h_mcg_ctl )
> +        return 1;
> +
> +    bank_nr = bank->mc_bank;
> +    if (~d->arch.vmca_msrs.mci_ctl[bank_nr] & h_mci_ctrl[bank_nr] )
> +        return 1;
> +    return 0;
> +}
> +
>  static int x86_mc_msrinject_verify(struct xen_mc_msrinject *mci)
>  {
>       struct cpuinfo_x86 *c;
> diff -r b2a7600b71cc xen/arch/x86/cpu/mcheck/mce.h
> --- a/xen/arch/x86/cpu/mcheck/mce.h   Tue Jan 26 00:52:19 2010 +0800
> +++ b/xen/arch/x86/cpu/mcheck/mce.h   Tue Jan 26 00:52:20 2010 +0800
> @@ -39,6 +39,8 @@ void amd_nonfatal_mcheck_init(struct cpu
>  void amd_nonfatal_mcheck_init(struct cpuinfo_x86 *c);
>
>  u64 mce_cap_init(void);
> +extern int firstbank;
> +int mca_ctl_conflict(struct mcinfo_bank *bank, struct domain *d);
>
>  int intel_mce_rdmsr(uint32_t msr, uint64_t *val);
>  int intel_mce_wrmsr(uint32_t msr, uint64_t val);
> diff -r b2a7600b71cc xen/arch/x86/cpu/mcheck/mce_intel.c
> --- a/xen/arch/x86/cpu/mcheck/mce_intel.c     Tue Jan 26 00:52:19 2010 +0800
> +++ b/xen/arch/x86/cpu/mcheck/mce_intel.c     Tue Jan 26 00:52:20 2010 +0800
> @@ -20,7 +20,6 @@ int ser_support = 0;
>  int ser_support = 0;
>
>  static int nr_intel_ext_msrs = 0;
> -static int firstbank;
>
>  /* Below are for MCE handling */
>  struct mce_softirq_barrier {
> @@ -361,7 +360,15 @@ static void intel_UCR_handler(struct mci
>                         *  the mfn in question) */
>                        BUG_ON( result->owner == DOMID_COW );
>                        if ( result->owner != DOMID_XEN ) {
> +
>                            d = get_domain_by_id(result->owner);
> +                          if ( mca_ctl_conflict(bank, d) )
> +                          {
> +                              /* Guest has different MCE ctl with
> hypervisor */ +                              put_domain(d);
> +                              return;
> +                          }
> +
>                            gfn =
>                                mfn_to_gmfn(d, ((bank->mc_addr) >>
> PAGE_SHIFT)); bank->mc_addr =



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